For some car models, particularly those manufactured by Mercedes-Benz, the car hood has the grill attached to the car hood. Thus, when the car hood is raised, the grill is also raised. In performing engine repairs upon such a car, quick upward movements by the mechanic can result in the mechanic striking his head against the raised grill. As the grill may have some sharp corners, cuts or lacerations may result to the head of the mechanic when the grill is accidentally struck.
While it is possible for the mechanic to exercise care while working over an engine, if startled or surprised, the mechanic may suddenly straighten up and strike his head. Since most cars do not have the grill depending from the hood, the owners or mechanics are used to lifting their heads without hitting their heads on the grill. A helmet worn on the head of the mechanic would protect the mechanic's head, but helmets are bulky, heavy, hot, and generally inconvenient.